Blood Test Narrows Down Need for Antibiotics

Could lead to better treatment decisions for respiratory infections, experts say

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TUESDAY, Sept. 8, 2009 (HealthDay News) -- A simple blood test may be able to help doctors determine which patients need antibiotics and which do not.

A new study published in the Sept. 9 issue of the Journal of the American Medical Association found that use of the test resulted in less antibiotic use.

If the protocol winds up in widespread use, it could significantly cut down on side effects associated with antibiotic use, not to mention slowing the spread of "killer" bacteria which become stubbornly resistant to these medications.

"It certainly holds a lot of promise," said Dr. Donald M. Yealy, co-author of an editorial accompanying the study and chair of emergency medicine at the University of Pittsburgh. "We need a way to make a better determination of need."

Overzealous use of antibiotics is commonly acknowledged as the main factor driving microbial resistance worldwide.

"What's not disputed is that antibiotics have changed health," Yealy said. "But there's also no doubt that they're currently often overused."

"I think this is very exciting," said Dr. Ann Falsey, a professor of medicine at the University of Rochester Medical Center who specializes in infectious disease. "There's been a great deal of antibiotic overuse, with a great number of adverse effects both to patients individually and to the global flora becoming more resistant. This is one tool that can help clinicians make better decisions."

According to background information in the article, in the northwestern hemisphere antibiotics are most often prescribed for lower respiratory tract infections (LRTIs). LRTIs can mean anything from bronchitis, which is likely to go away on its own, to community-acquired pneumonia (CAP), which can be life-threatening.

Up to three-quarters of LRTI patients are treated with antibiotics, even though most of these infections are viral and don't respond to antibiotics. There is some indication that the use of antibiotics has declined in children over the past 12 years, research released last month suggested.

This Swiss team randomly assigned almost 1,400 patients with LRTIs who came to emergency rooms at six hospitals to receive antibiotics based on results of a PCT test, or based on standard guidelines.

PCT stands for procalcitonin, a chemical found in the blood. The test was provided by BRAHMS Inc., which makes the test.

Patients in the PCT group were on antibiotics for shorter periods of time: 5.7 days vs. 8.7 days in the control group. The same pattern held true in the subgroups of patients with CAP (7.2 days in the PCT group vs. 10.7 days in the control group); those with chronic obstructive pulmonary disease (2.5 vs. 5.1 days); and those with acute bronchitis (1 day vs. almost 3 days). Fewer people in the PCT group had adverse events (19.8 percent vs. 28.1 percent).

But the test has a few hurdles to pass before it can be widely adopted, experts stated.

"It's a nice initial clinical trial, but we need to see if it will change behavior," Yealy said. "We also don't know if this will apply to other settings."

Most of the patients in this trial had pneumonia and many of them had severe pneumonia, a group which often does need antibiotics.

The bigger issue is use in less ill populations, said Yealy, who tells of a recent promotion by a local supermarket chain promising free generic antibiotics to people with prescriptions.

"There is pressure to increase antibiotic use," he said.

"I'm cautiously optimistic," said Dr. Lilian Abbo, an assistant professor of infectious diseases at the University of Miami Miller School of Medicine. "It's unclear if we can extrapolate the findings. The study was conducted in Switzerland, it was an elderly population, and a high number had pneumonia. More studies are needed to interpret this and to incorporate it into practice."

The test is available in the United States, but is not approved for this purpose, Yealy said.

"This was one specific manufacturer's test," Yealy noted. "It may not apply to others."